The present invention relates first to an illumination device for an observation device according to the preamble of patent claim 1. In addition, the invention relates to an observation device according to the preamble of patent claim 17.
For example, an observation device may involve an operating microscope. In particular, the observation device can be designed as an ophthalmologic operating microscope, which is utilized, for example, for a special application in eye surgery, i.e., cataract surgery.
In the case of cataract surgery, a lens of the eye—which is clouded, for example, due to the cataract—is replaced by an artificial lens.
The lens of an eye is found inside a thin envelope, the so-called lens capsule. In order to remove the lens of the eye, access to the lens is created by a thin incision made in the lens capsule and the lens of the eye is next broken up into small pieces with a microsurgical instrument, and then these pieces are removed by means of an aspirating device.
This process takes place under microscopic observation—for example, under stereomicroscopic observation—employing a specially designed illumination device for such interventions. This illumination device presents both an illumination of the surrounding field, which is necessary for illuminating the entire operating field, as well as a red background illumination for the actual operating field limited to the pupil region of the lens of the eye, which is of decisive importance for the cataract operation. This red background illumination is based on the fraction of illuminating light, which, passing through the transparent media of the eye finally strikes the retina, which appears red due to good blood perfusion, is reflected therefrom, and then can also be observed, of course, as an apparent red background illumination, by the surgeon via the operating microscope. This very characteristic red background illumination in cataract surgery is generally known in professional circles under the term “red reflex”.
For an optimal recognition of details relevant to the cataract operation, a red background illumination that is as homogeneous as possible has been proven to be a necessary prerequisite for the surgeon. A first requirement of the illumination device is thus to assure a homogeneity of the red reflex that is as optimal as possible over the entire pupil of the patient.
For complete elimination of the lens pieces of the lens of the eye, which has been broken up into tiny pieces, and for good recognition of transparent membranes, for example, of the lens capsule, another requirement must be fulfilled, that is, a good contrasting of phase objects and, in fact, this contrast should also be provided as much as possible over the entire pupil of the patient.
For surgery on the eye, and here, in particular, in cataract operations, a homogeneous, bright “red reflex” is required along with a good contrasting of phase objects over the entire region of the patient's pupil.
The operating microscopes of the prior art fulfill these requirements for regions of the pupil that are of varying size. A compromise must always be found between the primary requirements of a good, homogeneous “red reflex” and good contrasting of phase objects.
For the most part, illumination is provided at a small angle to the observation. This has the consequence, however, that the “red reflex” does not appear uniformly bright over the patient's pupil. An illuminating angle between 2 and 4 degrees has previously proven favorable. At this angle, one obtains a good compromise between good contrasting and illumination of the patient's pupil. Solutions, in which illumination is made at an angle to the observation, are described, for example, in DE 43 44 770 A1 or DE 20 2004 019 849 U1. With this arrangement, however, the “red reflex” reacts sensitively to a rolling of the patient's eye during the operation. Additional problems may occur when the patient's pupil is small or in connection with the refraction of the patient's eye. In the known solutions, therefore, the “red reflex” is not formed homogeneously.
For eye surgery, particularly in cataract surgeries, however, the surgeon requires a homogeneous, contrast-rich “red reflex”.
Tests with coaxial illumination in fact led to a good, homogeneous “red reflex”, but to a poor contrasting of phase objects, and thus previously have not proven suitable in practice. In this case, the illuminating optics unit was disposed in such a way that an illuminating mirror (or prism) lay between the two beam paths of the stereomicroscope. Thus, this did not involve an exact 0° illumination, which occurs precisely from the same direction as the observation.
One possibility for obtaining a homogeneous, bright “red reflex” with simultaneously good contrast can be achieved by providing an illumination device for an observation device having one, two or more observation beam paths, each with at least one observation beam bundle, in particular, for an operating microscope, having at least one light source for producing at least one illumination beam path with at least one illumination beam bundle for illuminating an object to be observed, in particular, an eye to be observed, whereby the illumination device has at least one illumination optics unit that is constructed according to the Köhler principle of illumination, and whereby the at least one illumination beam path or the at least one illumination beam bundle runs coaxially to an observation beam path or observation beam bundle. Such a solution is described, for example, in the older Application DE 10 2006 013 761.2 A1 of the Applicant.
In many cases, however, only a small structural space is present for the illumination device, so that an illumination optics unit, which is constructed according to the Köhler principle of illumination, cannot always be used.